Ureteropelvic junction obstruction (UPJO) is defined as functional or anatomic obstruction of urine flow from the renal pelvis into the ureter. UPJO may be caused by intrinsic or extrinsic anatomic anomalies classified as congenital, acquired, or by functional impedance of urinary flow across the ureteropelvic junction (UPJ). Intrinsic causes of obstruction include congenital narrowing at the UPJ caused by a defect in ureteral musculature, persistent mucosal folds, high insertion of the ureter into the renal pelvis, and (rarely) ureteral polyps. Congenital extrinsic obstruction is usually caused by a crossing vessel, typically an accessory or aberrant arterial branch supplying the lower pole. Acquired obstruction is the result of fibrosis caused by ischemia from previous ureteral surgery, stone impaction, or traumatic injury, or it may be caused by lymphadenopathy.
Historically, UPJO was corrected by open dismembered pyeloplasty with a high success rate. However, minimally invasive approaches have largely supplanted open surgery and include laparoscopic and robotic surgery and percutaneous or ureteroscopic endopyelotomy. Minimally invasive pyeloplasty has emerged as the gold-standard treatment for primary UPJO with the best and most durable outcomes. However, endopyelotomy still has a role as first-line treatment for select patients with primary UPJO and for patients with secondary UPJO. Endopyelotomy, in which a full-thickness incision is carried through the narrowed segment from normal ureter proximally into normal ureter distally, can be accomplished via a single-stage antegrade or retrograde approach using a cold knife, electrosurgical probe, or holmium laser. Retrograde or antegrade use of a ureteral cutting balloon (Acucise; Applied Urology, Rancho Santa Margarita, CA) has largely been abandoned in lieu of the safer direct vision endopyelotomy. The overall success rate for retrograde ureteroscopic endopyelotomy ranges from 67% to 86% and is negatively impacted by the presence of a crossing vessel, massive hydronephrosis, and poor ipsilateral renal function.
Benign ureteral strictures are most commonly caused by iatrogenic injury during ureteroscopic surgery, although they can also be associated with highly impacted calculi or external inflammatory processes that lead to fibrosis and stricture formation. Benign ureteroenteric anastomotic strictures are typically the result of ischemia occurring after reimplantation of the ureter into the bowel segment. Ureteral and ureteroenteric strictures can be managed with laparoscopic or robotic ureteroureterostomy, ureteral reimplantation, buccal mucosal graft ureteroplasty, or percutaneous or ureteroscopic endoureterotomy.
Primary UPJO is most successfully treated with minimally invasive pyeloplasty. Patients with recurrent UPJO after failed pyeloplasty and those with secondary UPJO, however, are candidates for ureteroscopic endopyelotomy. Absolute contraindications to ureteroscopic endopyelotomy include active urinary tract infection and uncorrected bleeding diatheses. The presence of a crossing vessel, large renal pelvis, concurrent renal calculi, ipsilateral differential renal function less than 20%, length of the narrow segment exceeding 2 cm, and stent intolerance comprise relative contraindications, and patients with these characteristics may be better served with repeat pyeloplasty or other reconstructive alternatives.
Endoureterotomy is considered the first-line treatment for ureteral strictures shorter than 1 cm. However, success rates decline for strictures longer than 1 cm and strong consideration should be given to laparoscopic or robotic or open reconstruction for patients with longer strictures.
Preoperative ureteral stenting may alleviate flank pain, improve renal function, and passively dilate the ureter, thus facilitating ureteral access at the time of endopyelotomy or endoureterotomy, but this measure is not a necessary step in the procedure. Furthermore, preoperative stenting may make delineation of the stricture more difficult. Preoperative imaging with a helical computed tomography (CT) angiogram in patients with UPJO is advisable to identify a crossing vessel that may preclude safe endoscopic incision or negatively impact outcomes. For patients undergoing endoureterotomy, retrograde and, in some cases, additional antegrade imaging studies should be obtained to assess stricture location, length, and severity. Antegrade studies may include CT or intravenous urography, or if the patient has a nephrostomy tube, an antegrade nephrostogram can be obtained. Knowledge of the ureteral blood supply in relation to the location of the stricture is important when considering endoscopic incision so as to avoid compromising the blood supply and causing bleeding. The recommended direction of incision is lateral for proximal ureteral strictures, anterior to anteromedial for middle ureteral strictures, medial for distal strictures, and anterior for intramural strictures. In the case of previous reconstruction for urologic malignancy, tumor recurrence should be excluded before endoscopic incision, particularly in the case of ureteroenteric strictures that develop after surgery for urothelial carcinoma.
Urine culture should be obtained in all patients, and culture-specific antibiotics are administered to those with positive culture results. Sterile urine must be documented before surgery. Coagulation studies are obtained only as indicated by a history of bleeding diathesis, and in those with abnormal findings, a formal hematology evaluation may be requested. On the day of the procedure, a parenteral antibiotic is administered in time to achieve therapeutic plasma levels before the intervention. The procedure can be performed under general or spinal anesthesia, although general anesthesia is preferred.
Ureteroscopic Endopyelotomy: the Procedure
After placement of antiembolic stockings or pneumatic compression devices, the patient is placed on a radiolucent table in the modified dorsal lithotomy position, and all pressure points are carefully padded.
A rigid cystoscope is introduced into the bladder and a retrograde pyelogram is performed to delineate anatomy of the ureter and the UPJ, particularly defining the area of obstruction ( Fig. 43.1 ). A total of 15 to 20 mL of dilute contrast may be necessary to adequately opacify the dilated renal pelvis.
A 0.035-inch Bentson guidewire is passed into the ureteral orifice and advanced up the ureter under fluoroscopic guidance until it coils in the renal pelvis ( Fig. 43.2 ). A second, stiff-shafted guidewire is passed into the renal pelvis using an 8/10-Fr coaxial introducer or a dual-lumen catheter ( Fig. 43.3 ). The Bentson wire is secured to the drape as a safety wire to safeguard against lost ureteral access, and the stiff wire is used to deliver a ureteral access sheath just distal to the UPJ. The working guidewire is removed. An actively deflectable flexible ureteroscope is then inserted through the sheath and passed up to the level of the UPJ ( Fig. 43.4 ). Although a ureteral access sheath is optional, it helps to reduce intrarenal pelvic pressure and improve visibility.
The entire UPJ segment is then examined circumferentially to define the length of stricture and identify transmitted ureteral wall pulsations from a possible crossing vessel.
A 200- or 273-micron holmium:yttrium-aluminum-garnet (Ho:YAG) laser fiber is passed through the working channel of the ureteroscope until the tip of the fiber is visible in the field of view of the ureteroscope ( Fig. 43.5 ). Using an energy setting of 1.0 J and a frequency of 10 to 15 Hz, a straight lateral incision is made that extends from the renal pelvis proximally into patent, healthy ureter distal to the narrowed segment. The incision should extend 1 cm proximal and distal to the narrowed segment into normal pelvis or ureter and should be carried through the full thickness of the ureteral wall into periureteral fat, incising the ureter layer by layer (see Fig. 43.5 ). The ureteroscope is then removed, and a 4-cm, 15–24-Fr dilating balloon is passed over the guidewire to calibrate the incised segment and separate the cut edges ( Fig. 43.6 ). The balloon should fully inflate at low pressure (2–3 Atm) if the incision is sufficiently deep and long ( Fig. 43.7 ).